The study on allorecognition in colonial animals

1.两种日本海绵，Hilichondria okadai和H.Japonica，表现出异源识别反应。一个个体的一部分与同一个体的另一部分融合，但不与另一个个体的一部分融合。这表明控制同种异体识别的基因表现出高度多态性。相反，来自单个雌性个体的幼虫之间的融合率非常高。在幼虫中，同种识别机制可能还不成熟，不能排斥不亲和的幼虫.苔藓虫群落表现出异源识别反应。沿着两个接触群体的边界观察到虫囊的融合或破坏.已有研究表明，当两个不相容的菌落融合时，海鞘会表现出延迟的同种识别反应。这种反应被称为“群体再吸收”，葡萄螺类动物表现出这种反应的层次性。很明显，异源识别能力在群体无脊椎动物中是普遍的。然而，目前还不清楚是否只有群体动物通过进化过程保持了识别能力，或者这种能力是所有动物的共同和基本功能。为了与脊椎动物的MHC进行比较，我们需要对海绵动物和苔藓动物的同种异体识别的遗传学进行大量的研究，并且还需要对许多其他门动物的同种异体识别的存在进行检查。

1. The two species of Japanese sponges, Hilichondria okadai and H.Japonica, showed allorecognition responses. A piece of an individual fused with another piece of the same individual, but did not fuse with the piece of the other individual. This suggests that the genes controlling allorecognition show high polymorphism. On the contrary, the rate of fusion among larvae from a single female individual was very high. In a larva the mechanism of allorecognition might be too immature to reject incompatible larvae.2. Bryozoan colonies showed allorecognition responses. Fusion or destruction of zooeciums was observed along the boundary between two contact colonies.3. It was already reported that botryllid ascidians show the delayd allorecognition responses when two incompatible colonies has fused. This responses are called "colony resorption", and botryllids display a hierarchy of this responses.It becomes clear that the ability of allorecognition is common among colonial invertebrates. However, it is unclear whether the ability of allorecognition has been kept in only colonial animals through their evolution processes or that ability is a common and basic function for all animals. We need much study on the genetics of allorecognition in sponges and bryozoans in order to compare with MHC of vertabrates, and also need examination of many animals of other phylum about the presence of allorecognition.